US20090306518A1 - Transducers, devices and systems containing the transducers, and methods of manufacture - Google Patents

Abstract

A catheter assembly for an intravascular ultrasound system includes a catheter and an imaging core. The catheter includes a lumen extending along the longitudinal length of the catheter from the proximal end to the distal end and the imaging core is configured and arranged for inserting into the lumen. The imaging core includes a rotatable driveshaft, at least one transducer mounted to the distal end of the rotatable driveshaft, and a twisted wire cable coupled to the at least one transducer. In addition, a number of different transducer arrangements and methods of making transducers are presented

Description

CROSS REFERENCE TO RELATED APPLICATION
• This application claims priority of U.S. Provisional Patent Application Ser. No. 61/059,431, filed on Jun. 6, 2008, the entire contents of which is hereby incorporated by reference.
TECHNICAL FIELD
• The present invention is directed to the area of transducers for ultrasound imaging systems, devices and systems containing the transducers, and methods of making and using the transducers. The present invention is also directed to transducers for an intravascular ultrasound imaging system.
BACKGROUND
• Intravascular ultrasound (“IVUS”) imaging systems have proven diagnostic capabilities for a variety of diseases and disorders. For example, IVUS imaging systems have been used as an imaging modality for diagnosing blocked blood vessels and providing information to aid medical practitioners in selecting and placing stents and other devices to restore or increase blood flow. IVUS imaging systems have been used to diagnose atheromatous plaque build-up at particular locations within blood vessels. IVUS imaging systems can be used to determine the existence of an intravascular obstruction or stenosis, as well as the nature and degree of the obstruction or stenosis. IVUS imaging systems can be used to visualize segments of a vascular system that may be difficult to visualize using other intravascular imaging techniques, such as angiography, due to, for example, movement (e.g., a beating heart) or obstruction by one or more structures (e.g., one or more blood vessels not desired to be imaged). IVUS imaging systems can be used to monitor or assess ongoing intravascular treatments, such as angiography and stent placement in real (or almost real) time. Moreover, IVUS imaging systems can be used to monitor one or more heart chambers.
• IVUS imaging systems have been developed to provide a diagnostic tool for visualizing a variety is diseases or disorders. An IVUS imaging system can include a control module (with a pulse generator, an image processor, and a monitor), a catheter, and one or more transducers disposed in the catheter. The transducer-containing catheter can be positioned in a lumen or cavity within, or in proximity to, a region to be imaged, such as a blood vessel wall or patient tissue in proximity to a blood vessel wall. The pulse generator in the control module generates electrical pulses that are delivered to the one or more transducers and transformed to acoustic pulses that are transmitted through patient tissue. Reflected pulses of the transmitted acoustic pulses are absorbed by the one or more transducers and transformed to electric pulses. The transformed electric pulses are delivered to the image processor and converted to an image displayable on the monitor.
BRIEF SUMMARY
• One embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy. The transducer element further comprises a first non-transducing pad defined in the transducer element. The ultrasound transducer also includes a first metal layer substantially disposed over a first surface of the transducer element and over the first non-transducing pad; and a second metal layer substantially disposed over a second surface of the transducer element.
• Another embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy; a first metal layer substantially disposed over a first surface of the transducer element; a second metal layer substantially disposed over a second surface of the transducer element (the second surface opposing the first surface); a backing layer disposed over the second metal layer; and a third metal layer disposed over the backing layer. The third metal layer defines a first contact and a second contact that are separated from each other. The first contact is coupled to the first metal layer by a first contact via and the second contact is coupled to the second metal layer by a second contact via.
• Yet another embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy. The ultrasound transducer further includes a first thin film circuit comprising a first substrate with metal traces disposed on opposing sides of the first substrate and electrically coupled together. The metal traces are configured and arranged to provide a contact pad on one side of the first substrate and an electrode for providing electrical signals to the transducer element on another side of the first substrate. The ultrasound transducer also includes a second thin film circuit comprising a second substrate with metal traces disposed on opposing sides of the second substrate and electrically coupled together. The metal traces are configured and arranged to provide a contact pad on one side of the second substrate and an electrode for providing electrical signals to the transducer element on another side of the second substrate. The transducer element is disposed between the first and second thin film circuits.
• A further embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy; a carrier substrate comprising a first surface and a second surface opposing the first surface; a first metal layer disposed on the first surface of the carrier substrate and defining a first contact and a second contact that are separate from each other; a second metal layer disposed on the second surface of the carrier substrate and in electrical communication with the second contact on the first surface of the carrier substrate; a third metal layer; and a conducting structure electrically coupling the first contact with the third metal layer. The transducer element is disposed between the second metal layer and the first metal layer. The conducting structure itself is electrically insulated from the transducer element.
• Another embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy. The transducer element has a first surface, a second surface opposing the first surface, and an edge surface between the first and second surfaces. The ultrasound transducer further includes a first metal layer disposed over the first surface of the transducer element; a second metal layer disposed over the second surface of the transducer element; a first contact extending from the first metal layer along a first portion of the edge surface of the transducer element; and a second contact extending from the first metal layer along a second portion of the edge surface of the transducer element.
• Yet another embodiment is a method of making an ultrasound transducer including forming at least one first vertical slot extending from a first surface partway through a transducer element. Metal is disposed within the first vertical slot(s) to at least coat exposed surfaces of the transducer element within the first vertical slot(s). A first metal layer is disposed over the first surface of the transducer element and in contact with the metal disposed within the first vertical slot(s). At least one second vertical slot is formed extending from a second surface partway through the transducer element. The second surface of the transducer element opposes the first surface of the transducer element. Metal is disposed within the second vertical slot(s) to at least coat exposed surfaces of the transducer element within the second vertical slot(s). A second metal layer is disposed over the second surface of the transducer element and in contact with the metal disposed within the second vertical slot(s). The transducer element is cut through the first and second vertical slots to form an ultrasound transducer with first and second contacts formed from the metal disposed in the first and second vertical slots, respectively.
• A further embodiment is a catheter assembly for an intravascular ultrasound system that includes a catheter and an imaging core. The catheter has a longitudinal length, a distal end, and a proximal end. The catheter also includes a lumen extending along the longitudinal length of the catheter from the proximal end to the distal end. The imaging core is configured and arranged for inserting into the lumen. The imaging core includes a rotatable driveshaft having a distal end and a longitudinal length, at least one transducer mounted to the distal end of the rotatable driveshaft, and a twisted wire cable. The at least one transducer is configured and arranged for transforming applied electrical pulses to acoustic pulses and also for transforming received echo pulses to electrical pulses. The twisted wire cable includes i) two wires running along the cable and electrically coupled to respective contacts of the at least one transducer, and ii) a shield extending along the cable and within which a portion of the two wires are disposed.
BRIEF DESCRIPTION OF THE DRAWINGS
• Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings. In the drawings, like reference numerals refer to like parts throughout the various figures unless otherwise specified.
• For a better understanding of the present invention, reference will be made to the following Detailed Description, which is to be read in association with the accompanying drawings, wherein:
• FIG. 1 is a schematic view of one embodiment of an intravascular ultrasound imaging system, according to the invention;
• FIG. 2 is a schematic side view of one embodiment of a catheter of an intravascular ultrasound imaging system, according to the invention;
• FIG. 3 is a schematic perspective view of one embodiment of a distal end of an elongated member of the catheter shown inFIG. 2 with an imaging core disposed in a lumen in the distal end of the elongated member, according to the invention;
• FIG. 4 is schematic side view of one embodiment of a tip of a catheter with a transducer and a twisted pair cable, according to the invention;
• FIG. 5 is a schematic side view of one embodiment of a tip of a catheter with a modular arrangement for attachment of a transducer, according to the invention;
• FIG. 6 is a schematic perspective view of one embodiment of a transducer element with non-transducing pads, according to the invention;
• FIG. 7 is a schematic perspective view of one embodiment of a transducer with the transducer element ofFIG. 6, according to the invention;
• FIG. 8 is a schematic top view of one embodiment of an arrangement containing multiple transducers ofFIG. 7, according to the invention;
• FIG. 9 is a schematic top view of another embodiment of an arrangement containing multiple transducers, according to the invention;
• FIG. 10 is a schematic perspective view of one embodiment of a transducer ofFIG. 9 with the transducer element ofFIG. 6, according to the invention;
• FIGS. 11A and 11B are schematic front and back side views of a further embodiment of a transducer, according to the invention;
• FIGS. 11C,11D, and11E are schematic top views of first, second, and third metal layers of the transducer ofFIGS. 11A and 11B, also illustrating the arrangement of multiple transducers (separated by the dotted lines), according to the invention;
• FIG. 12 is a schematic cross-sectional view of a fourth embodiment of a transducer, according to the invention;
• FIGS. 13A-13G are schematic cross-sectional views of steps in one embodiment of a method of making the transducer ofFIG. 12, according to the invention;
• FIG. 14A is a schematic partial exploded view of an arrangement of multiple transducers corresponding to a fifth embodiment according to the invention;
• FIGS. 14B and 14C are schematic front and side views of the transducer ofFIG. 14A, according to the invention;
• FIG. 15A is a schematic exploded view of a sixth embodiment of a transducer, according to the invention;
• FIG. 15B is a schematic cross-section view of the transducer ofFIG. 15A, according to the invention;
• FIG. 16 is a schematic cross-sectional view of a seventh embodiment of a transducer, according to the invention; and
• FIGS. 17A-17F are schematic cross-sectional views of steps in one embodiment of a method of making the transducer ofFIG. 16, according to the invention.
DETAILED DESCRIPTION
• The present invention is directed to the area of transducers for ultrasound imaging systems, devices and systems containing the transducers, and methods of making and using the transducers. The present invention is also directed to transducers for an intravascular ultrasound imaging system.
• Suitable intravascular ultrasound (“IVUS”) imaging systems include, but are not limited to, one or more transducers disposed on a distal end of a catheter configured and arranged for percutaneous insertion into a patient. Examples of IVUS imaging systems with catheters are found in, for example, U.S. Pat. Nos. 7,246,959; 7,306,561; and 6,945,938; as well as U.S. Patent Application Publication Nos. 20060253028; 20070016054; 20060106320; 20070038111; 20060173350; and 20060100522, all of which are incorporated by reference.
• FIG. 1 illustrates schematically one embodiment of anIVUS imaging system100. TheIVUS imaging system100 includes acatheter102 that is coupleable to acontrol module104. Thecontrol module104 may include, for example, aprocessor106, apulse generator108, amotor110, and one ormore displays112. In at least some embodiments, thepulse generator108 forms electric pulses that may be input to one or more transducers (312 inFIG. 3) disposed in thecatheter102. In at least some embodiments, mechanical energy from themotor110 may be used to drive an imaging core (306 inFIG. 3) disposed in thecatheter102. In at least some embodiments, electric pulses transmitted from the one or more transducers (312 inFIG. 3) may be input to theprocessor106 for processing. In at least some embodiments, the processed electric pulses from the one or more transducers (312 inFIG. 3) may be displayed as one or more images on the one ormore displays112. In at least some embodiments, theprocessor106 may also be used to control the functioning of one or more of the other components of thecontrol module104. For example, theprocessor106 may be used to control at least one of the frequency or duration of the electrical pulses transmitted from thepulse generator108, the rotation rate of the imaging core (306 inFIG. 3) by themotor110, the velocity or length of the pullback of the imaging core (306 inFIG. 3) by themotor110, or one or more properties of one or more images formed on the one ormore displays112. In some embodiments, the parts of the control module104 (i.e., theprocessor106, thepulse generator108, themotor110, and the one or more displays112) may be in one unit. In other embodiments, the parts of thecontrol module104 are in two or more units.
• FIG. 2 is a schematic side view of one embodiment of thecatheter102 of the IVUS imaging system (100 inFIG. 1). Thecatheter102 includes anelongated member202 and ahub204. Theelongated member202 includes aproximal end206 and adistal end208. InFIG. 2, theproximal end206 of theelongated member202 is coupled to thecatheter hub204 and thedistal end208 of the elongated member is configured and arranged for percutaneous insertion into a patient. In at least some embodiments, thecatheter102 defines at least one flush port, such asflush port210. In at least some embodiments, theflush port210 is defined in thehub204. In at least some embodiments, thehub204 is configured and arranged to couple to the control module (104 inFIG. 1). In some embodiments, theelongated member202 and thehub204 are formed as a unitary body. In other embodiments, theelongated member202 and thecatheter hub204 are formed separately and subsequently assembled together.
• FIG. 3 is a schematic perspective view of one embodiment of thedistal end208 of theelongated member202 of thecatheter102. Theelongated member202 includes asheath302 and alumen304. Animaging core306 is disposed in thelumen304. Theimaging core306 includes animaging device308 coupled to a distal end of arotatable driveshaft310.
• Thesheath302 may be formed from any flexible, biocompatible material suitable for insertion into a patient. Examples of suitable materials include, for example, polyethylene, polyurethane, polytetrafluoroethylene (PTFE), other plastics, and the like or combinations thereof.
• One ormore transducers312 may be mounted to theimaging device308 and employed to transmit and receive acoustic pulses. In a preferred embodiment (as shown inFIG. 3), an array oftransducers312 are mounted to theimaging device308. In other embodiments, a single transducer may be employed. In yet other embodiments, multiple transducers in an irregular-array may be employed. Any number oftransducers312 can be used. For example, there can be two, three, four, five, six, seven, eight, nine, ten, twelve, fifteen, sixteen, twenty, twenty-five, fifty, one hundred, five hundred, one thousand, or more transducers. As will be recognized, other numbers of transducers may also be used.
• The one ormore transducers312 may be formed from one or more known materials capable of transforming applied electrical pulses to pressure distortions on the surface of the one ormore transducers312, and vice versa. Examples of suitable materials include piezoelectric ceramic materials, piezocomposite materials, piezoelectric plastics, barium titanates, lead zirconate titanates, lead metaniobates, polyvinylidenefluorides, lead magnesium niobate-lead titanates, and the like. These materials will be collectively referred to as “piezoelectric materials”. Additionally, capacitive micromachined ultrasound transducers (CMUTs) or the like may be used.
• Pressure distortions on the surface of the one ormore transducers312 can be generated in order to form acoustic pulses of a frequency based on the resonant frequencies of the one ormore transducers312. The resonant frequencies of the one ormore transducers312 may be affected by the size, shape, and material used to form the one ormore transducers312. The one ormore transducers312 may be formed in any shape suitable for positioning within thecatheter102 and for propagating acoustic pulses of a desired frequency or frequencies in one or more selected directions. For example, transducers may be disc-shaped, block-shaped, ring-shaped, layered, and the like. The one or more transducers may be formed in the desired shape by any process including, for example, dicing, machining, dice and fill, chemical etching, plasma etching, reactive ion etching, microfabrication, and the like.
• In at least some embodiments, the one ormore transducers312 can be used to form a radial cross-sectional image of a surrounding space. Thus, for example, when the one ormore transducers312 are disposed in thecatheter102 and inserted into a blood vessel of a patient, the onemore transducers312 may be used to form an image of the walls of the blood vessel and tissue surrounding the blood vessel.
• In at least some embodiments, theimaging core306 may be rotated about a longitudinal axis of thecatheter102. As theimaging core306 rotates, the one ormore transducers312 emit acoustic pulses in different radial directions. When an emitted acoustic pulse with sufficient energy encounters one or more medium boundaries, such as one or more tissue boundaries, a portion of the emitted acoustic pulse is reflected back to the emitting transducer as an echo pulse. Each echo pulse that reaches a transducer with sufficient energy to be detected is transformed to an electrical signal in the receiving transducer. The one or more transformed electrical signals are transmitted to the control module (104 inFIG. 1) where theprocessor106 processes the electrical-signal characteristics to form a displayable image of the imaged region based, at least in part, on a collection of information from each of the acoustic pulses transmitted and the echo pulses received. In at least some embodiments, the rotation of theimaging core306 is driven by themotor110 disposed in the control module (104 inFIG. 1).
• As the one ormore transducers312 rotate about the longitudinal axis of thecatheter102 emitting acoustic pulses, a plurality of images are formed that collectively generate a radial cross-sectional image of a portion of the region surrounding the one ormore transducers312, such as the walls of a blood vessel of interest and the tissue surrounding the blood vessel. In at least some embodiments, the radial cross-sectional image can be displayed on one ormore displays112.
• In at least some embodiments, theimaging core306 may also move longitudinally along the blood vessel within which thecatheter102 is inserted so that a plurality of cross-sectional images may be formed along a longitudinal length of the blood vessel. In at least some embodiments, during an imaging procedure the one ormore transducers312 may be retracted (i.e., pulled back) along the longitudinal length of thecatheter102. In at least some embodiments, themotor110 drives the pullback of theimaging core306 within thecatheter102. In at least some embodiments, themotor110 pullback distance of the imaging core is at least 5 cm. In at least some embodiments, themotor110 pullback distance of the imaging core is at least 10 cm. In at least some embodiments, themotor110 pullback distance of the imaging core is at least 15 cm. In at least some embodiments, themotor110 pullback distance of the imaging core is at least 20 cm. In at least some embodiments, themotor110 pullback distance of the imaging core is at least 25 cm.
• The quality of an image produced at different depths from the one ormore transducers312 may be affected by one or more factors including, for example, bandwidth, transducer focus, beam pattern, as well as the frequency of the acoustic pulse. The frequency of the acoustic pulse output from the one ormore transducers312 may also affect the penetration depth of the acoustic pulse output from the one ormore transducers312. In general, as the frequency of an acoustic pulse is lowered, the depth of the penetration of the acoustic pulse within patient tissue increases. In at least some embodiments, theIVUS imaging system100 operates within a frequency range of 1 MHz to 60 MHz.
• In at least some embodiments, one ormore conductors314 electrically couple thetransducers312 to the control module104 (SeeFIG. 1). In at least some embodiments, the one ormore conductors314 extend along a longitudinal length of therotatable driveshaft310.
• In at least some embodiments, thecatheter102 with one ormore transducers312 mounted to thedistal end208 of theimaging core308 may be inserted percutaneously into a patient via an accessible blood vessel, such as the femoral artery, at a site remote from the selected portion of the selected region, such as a blood vessel, to be imaged. Thecatheter102 may then be advanced through the blood vessels of the patient to the selected imaging site, such as a portion of a selected blood vessel.
• In many conventional transducer arrangements, the transducer is coupled to the remainder of the system using a coaxial cable. One contact of the transducer is coupled to the conductor that runs through the center of the coaxial cable and the other contact of the transducer is coupled to the cylindrical shield of the coaxial cable. Such an arrangement can lead to an unbalanced electrical connection between the transducer and the other electronic components of the ultrasound system.
• Moreover, the connections to the transducer are often made using conductive adhesive to avoid other wire attachment techniques, such as welding and soldering, that would raise the temperature of the heat-sensitive piezoelectric material of the transducer. Conductive adhesives, however, can be unreliable. For example, the adhesives may lose their ability to reliably attach the wires to the transducer when exposed to chemical sterilizing agents, such as ethylene oxide, which are often used to sterilize the ultrasound catheter between uses.
• FIG. 4 illustrates an alternative arrangement in which the transducer412, disposed in the catheter402, is coupled to the remainder of the electronics of the imaging system using a shielded twisted pair cable420. The shielded twisted pair cable420 includes two insulated wires422,424, that are twisted together along the cable, as well as a metal shield426 that can be electrically grounded. One of the wires422 can be coupled to a first contact of the transducer412 and the other wire424 can be coupled to a second contact of the transducer. This arrangement provides for a balanced electrical connection with the transducer. The transducer412 can be any transducer including currently available transducers. The wires420,422 can be attached to the transducer using any suitable method including conductive adhesives. As described in more detail below, the transducer can be arranged to allow the wires to be attached using heat-generating techniques, such as welding, soldering, thermal compression bonding, and the like.
• FIG. 5 illustrates another arrangement in which a transducer512, disposed in a catheter502, is coupled to a shielded twisted pair cable520 (with two wires522,524 and a conductive shield526) using a modular fitting530. In at least some embodiments of this arrangement, the transducer512 includes contacts (not shown) that couple (e.g., using a conductive adhesive or simply by contact) to corresponding contacts (not shown) on the modular fitting530. The contacts on the modular fitting530 are electrically coupled to pads (not shown) to which the wires522,524 can be attached. The wires522,524 can be attached to the pads of the modular fitting using any suitable technique. In particular, heat-generating techniques can be used for attachment of the wires522,524 because the piezoelectric material of the transducer is sufficiently distant that the heat will not damage it. In at least some instances, the wires may be attached to the modular fitting before the transducer is attached to the modular fitting. A modular arrangement, such as that illustrated inFIG. 5, may also allow the transducer512 to be removed or replaced without detaching the wires of the twisted pair cable520 from the transducer.
• There are a variety of arrangements and methods for forming a transducer. Typically, transducers have a number of different components including a transducer element, made of piezoelectric material or the like, that is disposed between at least two metal layers (or contact layers) through which electrical signals are provided to cause the transducer to emit ultrasound energy. The metal layers also receive electrical signals from the transducer element when the element receives ultrasound signals. The transducer may also optionally include at least one backing layer, and optionally, at least one matching layer.
• Any suitable transducer element can be used in the transducers disclosed herein. In general, the transducer element is made of a material, such as a piezoelectric material or the like, that converts electrical signals into ultrasound signals and vice versa. The transducer element, unless otherwise indicated, can be a single crystal transducer element or the transducer element can have one or more individual transducing members optionally separated by non-transducing material (see e.g.,FIG. 6) or any other suitable arrangement of transducing members.
• The metal layers and contact layers can be formed using any suitable conductive material including metals, alloys, and multi-layer conductive arrangements (e.g., multiple layers of different metals or alloys). Any metal or alloy can be used. For biological applications (e.g., intravascular ultrasound (IVUS) imaging), preferably any exposed portion of the metal or contact layers is made of a material (such as gold, platinum, platinum/iridium alloy, or silver-filled epoxy) that does not corrode when exposed to biological fluids under typical operating conductions. These materials may be plated over other metals, such as copper, Ni/Cr, Ni/Zn, and the like that may otherwise corrode. For example, copper or Ni/Cr can be covered by gold.
• The optional matching layer is made of a material that acoustically matches the transducer element to the biological environment. For example, the matching layer may facilitate matching the high acoustic impedance of the transducer element with the lower acoustic impedance of the surroundings, such as tissue and fluids within which the catheter is disposed. Any suitable material may be used including, but not limited to, parylene, epoxy, polyimide, other polymers, and the like.
• In some embodiments, the matching layer is non-conductive. In other embodiments, particularly when the matching layer is disposed between the transducer element and a metal layer, the matching layer is conductive. The matching layer can be made conductive by using, for example, a conductive polymer or by including conductive particles (e.g., metal, graphite, or alloy particles) within the polymeric material of the matching layer.
• The optional backing layer can be provided for a variety of purposes including, but not limited to, device stability, protection, acoustic matching, or acoustic absorption. The backing layer can be made using any suitable material including, but not limited to, parylene, epoxy, filled epoxies, other polymers, and the like. In some embodiments, the backing layer is non-conductive. In other embodiments, particularly when the backing layer is disposed between the transducer element and a metal layer, the backing layer is conductive. The backing layer can be made conductive by using, for example, a conductive polymer or by including conductive particles (e.g., metal, graphite, or alloy particles) within the polymeric material of the backing layer. Optionally, the backing layer may also function as a matching layer and be formed using a material that acoustically matches the transducer element.
• The backing and matching layers may be disposed on other layers of the transducer using any suitable method. Examples of methods for forming the backing and matching layers include, but are not limited to, spin coating, dip coating, spraying, vacuum deposition, chemical deposition, sputtering, casting, and the like or even adhering a pre-made backing or matching layer to another layer using an adhesive.
• FIG. 6 illustrates one embodiment of atransducer element602 that, when coupled to metal layers as described below, can be used to form a transducer. Thetransducer element602 includespiezoelectric material604 that forms multiple piezoelectric transducing members606. Each of the transducing members is separated from the others by non-transducing material610, such as epoxy, polyimide, silicon, alumina, and the like. In at least one embodiment, the transducer element is formed from a slab of piezoelectric material (typically disposed on a carrier) that is etched, scored, sliced, cut, diced, or otherwise separated into the individual transducing members. The non-transducing material may then be disposed between the transducing members using a suitable technique, such as coating methods.
• Thetransducer element602 also includes at least twonon-conductive pads608. Preferably, these pads are made of a heat-resistant material and, more preferably, are made of a material that does not readily conduct heat. For example, the pads can be made of epoxy, filled epoxy, and the like. For example, a low viscosity epoxy such as Epotek™ 301-2 (Epoxy Technology, Bilerica, Mass.) may be used. Thepads608 may be made of he same material as the non-transducing material610 and may be formed using the same techniques as are used to dispose the non-transducing material between the transducing members.
• Thesenon-conductive pads608 will be disposed below, or above, metal contact sites, as described in more detail below, so that the wires (see, e.g., wires422,424 ofFIG. 4) that couple the transducer to the remainder of the imaging system electronics can be attached using, for example, heat-based bonding techniques, such as, for example, laser welding, hot bar solder reflow, thermal compression bonding, gold ball bonding, other soldering or welding techniques, or other techniques that include the application of heat to attach the wires. Thenon-conductive pads608 provide protection from heat to the piezoelectric material of the transducing members so that these wire attachment techniques can be used.
• FIG. 7 illustrates one embodiment of atransducer700 that uses thetransducer element602 ofFIG. 6. Thetransducer element602 includes the piezoelectric material604 (formed as individual transducing members as illustrated inFIG. 6, although this detail is not shown inFIG. 7 for purposes of clarity) and thenon-conductive pads608. Thetransducer700 includes atop metal layer710 and abottom metal layer712. Ametal pad716 is disposed on the top of thetransducer element602, but is electrically isolated from thetop metal layer710 by a separation720 (e.g., by the removal of conductive material between the metal pad and the top metal layer.). Themetal pad716 is electrically coupled to thebottom metal layer712 through a conductive via718 that is formed by making a hole through at least thepad608 and plating or filling the hole with metal or another suitable electrically conducting material. Theportion714 of thetop metal layer710 and themetal pad716 are each disposed over one of thenon-conductive pads608 of thetransducer element602 and provide attachment sites for a wire (seeFIG. 4).
• The metal layers710,712 can be disposed on thetransducer element602 using any suitable method including, but not limited to, electroless plating, electroplating, evaporation, sputtering, chemical or physical vapor deposition, and the like. Theseparation720 between the top metalconductive layer710 and themetal pad716 can be formed using an suitable technique including patterning a metal layer disposed on the top of thetransducer element602 using a positive or negative photoresist and etching away, or otherwise removing, a portion of that metal layer to form thetop metal layer710 and themetal pad716 withseparation720. Alternatively, thetransducer element602 may be masked prior to the deposition of the metal so that theseparation720 is formed with the deposition of themetal layer710 andmetal pad716.
• The via718 can be formed by any suitable method including, but not limited to, drilling, plasma etching, chemical etching, laser ablating, sputter etching, or otherwise making a hole through at least thenon-conductive pad608 of the transducer element. In one embodiment, this hole is formed prior to disposing thetop metal layer710 or bottom metal layer712 (or both) on thetransducer element602 so that the hole can be coated or filled with metal as the top or bottom metal layer is formed. It will be understood, however, that the hole can be opened and the via718 coated or filled with metal after the top andbottom metal layers710,712 are formed.
• FIG. 8 illustrates one arrangement in which fourtransducers700a,700b,700c,and700dcan be formed together and then separated alonglines780,782. Such an arrangement permits the simultaneous patterning of a metal layer to form thetop metal layer710,metal pad716, andseparation720 for all four transducers. It will be recognized that this arrangement can be repeated as a larger arrangement to prepare more than four transducers together.
• FIG. 9 illustrates an alternate arrangement for forming fourtransducers700a′,700b′,700c′ and700d′. In this arrangement, instead of four vias, a single via718′ is provided. In addition, theseparation720′ between themetal layer710 andmetal pad716′ may be circular, rather than square or rectangular, although it will be understood that in any of the embodiments inFIGS. 7-10, the separation can have any shape as long as thetop metal layer710 andmetal pad716,716′ are not in electrical contact.FIG. 10 illustrates one of thetransducers700′ ofFIG. 9 with the same elements as thetransducer700 ofFIG. 7 except that aportion718′ of the side surface ofnon-conductive pad608 is coated with metal to electrically couple themetal pad716 to the bottom metalconductive layer712.
• Any of the embodiments inFIGS. 7-10 can be bonded to a backing layer (preferably, attached to the bottom metal layer). This backing layer may also be an acoustic matching layer. In addition, an acoustic matching layer may be disposed over at least a portion of the top metal layer.
• FIGS. 11A-11E illustrate yet another embodiment of atransducer750.FIGS. 11A and 11B are side views from opposing sides of the transducer. Thetransducer750 includes atransducing element752, a first patterned metal layer754 (FIG. 11C), a second patterned metal layer756 (FIG. 11D), a third patterned metal layer758 (FIG. 11E), and abacking layer760.FIGS. 11C-11E correspond to the first, second, and third patterned metal layers, respectively, and are illustrated in an arrangement for generating multiple transducers (similar to the arrangements inFIGS. 8 and 9). Each transducer corresponds to one of the rectangular regions bounded by the dotted lines (e.g.,lines762,764). Any transducer element can be used including, for example, thetransducer element602 ofFIG. 6 (although, for this embodiment, thepads608 are unnecessary and may be omitted or replaced with additional transducing elements.)
• In forming this transducer, vias766,768 are formed through all of the layers of the transducer and either coated or filled with metal or alloy. When the transducers are separated from each other, each via766,768 will be exposed similar to the via718′ inFIG. 10. In addition, aseparation770 is formed around via766 in thefirst metal layer754 and a separation is formed772 around via768 in thesecond metal layer756. In thethird metal layer758, aseparation774 divides thelayer758 into afirst contact776 and asecond contact778. The respective separations in each metal layer can be formed as each of the metal layers is deposited or the respective separations can be formed by patterning and etching (or otherwise removing a portion of the metal) a previously formed metal layer.
• The vias are generally made and coated/filled after forming each of the layers of the transducer. The via766 couples the majority ofsecond metal layer756 to thesecond contact778. The via768 couples the majority of thefirst metal layer754 to thefirst contact776. The wires from the remainder of the electronics of the ultrasound system can be connected to the first andsecond contacts776,778 (see, e.g.,FIG. 4). The presence of thebacking layer760 may permit the use of heat-based attachment methods for attaching the wires to the first andsecond contact776,778 by protecting thetransducer element750 from the heat generated by attachment. This embodiment also lends itself to electrical connection via preformed pads in the modular fitting530 shown inFIG. 5.
• FIG. 12 illustrates another arrangement of atransducer800 with atransducer element802 comprisingpiezoelectric regions804 separated bynon-piezoelectric regions806. Thetransducer800 also includes twometal layers808 and810; amatching layer812, and abacking layer814. Thetransducer800 is coupled to the remainder of the device electronics viacontact wires816 and818 that are disposed next to, or over, anon-piezoelectric region806′.
• FIGS. 13A-13G illustrate one embodiment of a method of making thetransducer800. It will be understood that a variety of other methods can be used to form thetransducer800. Apiezoelectric material804′ is removably attached to acarrier820 using any suitable technique including adhesives, waxes, and the like, as illustrated inFIG. 13A. Cuts are formed in thepiezoelectric material804′ to formpiezoelectric regions804, as illustrated inFIG. 13B. The cuts can be formed using any suitable technique including coating thepiezoelectric material804′ with a positive or negative photoresist; patterning and developing the photoresist to expose the portions of thepiezoelectric material804′ to be removed; and etching the exposed piezoelectric material to form the cuts. Other methods for forming the cuts include, for example, wet chemical etching, reactive ion etching, plasma etching, microdicing, and the like. After the cuts are formed, the cuts can be filled with a suitable non-piezoelectric material, such as, for example, epoxy, filled adhesive, or the like, to form thenon-piezoelectric regions806, as illustrated inFIG. 13B. Any suitable method for filling the cuts can be used including, for example, spin coating, dip coating, silkscreening, and the like. At least one of thenon-piezoelectric regions806′ is formed for later use in coupling awire816 to themetal layer808 over that region (seeFIG. 12) and may be larger than other non-piezoelectric regions.
• The exposed surface of thepiezoelectric regions804 andnon-piezoelectric regions806 is metallized to generatemetal layer810, as illustrated inFIG. 13C. The metallization can be performed using any suitable technique including, but not limited to, electroplating, electroless plating, sputtering, chemical or physical vapor deposition, and the like.
• Abacking layer814 is formed over themetal layer810, as illustrated inFIG. 13D. The backing layer can be formed using any suitable technique including casting, chemical or physical vapor deposition, coating (e.g., spin coating, dip coating, sputtering), and the like. The backing layer is typically formed using a non-conductive material and preferably is used to acoustically match the piezoelectric material.
• Thecarrier layer820 is removed, as illustrated inFIG. 13E. Asecond metal layer808 is formed over the exposed at least a portion of the exposed surface of thepiezoelectric regions804 andnon-piezoelectric regions806, as illustrated inFIG. 13F. The metallization can be performed using any suitable technique including, but not limited to, electroplating, electroless plating, sputtering, chemical or physical vapor deposition, and the like. Aportion822 of the exposed surface of thepiezoelectric regions804 may be left exposed by masking the portion of the surface prior to form themetal layer808. Alternatively or additionally, theportion822 of the exposed surface of thepiezoelectric regions804 may be exposed after forming themetal layer808 by patterning and etching the metal layer using, for example, a positive or negative photoresist.
• The exposedportion822 of thepiezoelectric region804 can be removed using an suitable technique, for example, selective etching the of thepiezoelectric material804, to expose a portion of theunderlying metal layer810, as illustrated inFIG. 13G. Amatching layer812 is disposed over themetal layer808 and, optionally, over the exposed portion of themetal layer810, as also illustrated inFIG. 13G. The matching layer can be formed by any suitable technique including, but not limited to, casting, chemical or physical vapor deposition, coating (e.g., spin coating, dip coating, sputtering), and the like. The matching layer is typically formed using a non-conductive material and is used to acoustically match the piezoelectric material.
• A portion of thematching layer812 is removed to exposed portions of themetal layer808 and810 to allow for attachment ofwires816 and818, as illustrated inFIG. 12. It should be noted that thewires816 and818 are not attached to portions of the metal layers808 and810 that are directly over or under apiezoelectric region804. Accordingly, in at least some embodiments, heat-based attachment methods can be used to attach thewires816 and818 to the metal layers808 and810.
• FIGS. 14A-14C illustrate anothertransducer900 with top and bottom flexible circuit layers902,904; atransducer element906; amatching layer908; and a backing layer910 (which may also function as a matching layer).FIG. 14A is a partially exploded view of one embodiment that includes multiple transducers that can be separated along the dotted lines.FIGS. 14B and 14C illustrate side views (taken along two orthogonal sides) of a single transducer.
• Thetransducer element906 may be a single crystal of piezoelectric material or any other suitable arrangement of piezoelectric material that can form a transducer element (see e.g., the transducer element ofFIG. 6 with or without the non-transducing pads). Thematching layer908 and can be formed using any suitable conductive material that is acoustically matched to the piezoelectric material. Thebacking layer910 can be formed using any suitable conductive material and may, in at least some embodiments, be acoustically matched to the piezoelectric material oflayer906.
• The flexible circuit layers902,904 are each formed from anon-conductive carrier substrate920,930, respectively, such as polyimide or any other suitable polymeric material, with metal traces922,924,932,934 formed on the top and bottom of the non-conductive carrier substrate and electrically coupled by at least one metallic via926,936 extending through thenon-conductive base920,930. The metal traces can be made using a single metal or alloy or can be made using layers of metals or alloys. The metal traces can be patterned or may cover an entire surface of the carrier substrate. In one embodiment, the conductive metal traces and vias are formed using copper and the exposed traces are then covered with Ni/Cr and then gold or another metal that is inert under physiological conditions. It will be understood that the via can be positioned anywhere within the flexible circuit layer (e.g., in the middle or along the edge of the flexible circuit layer).
• Wires can then be coupled to the flexible circuit layers902,904 to electrically connect the transducer to the remaining electronics of the ultrasound system. The flexible circuit, matching layer, and backing layer separate the wires from the transducer element to reduce heating of the transducer element if a heat-based bonding method is used to attach the wires to the transducer.
• FIGS. 15A and 15B illustrate another embodiment of atransducer1000. Thistransducer1000 includes atransducer element1002; a first metal layer forming separatedcontacts1008,1010; second andthird metal layers1004,1006;backing layer1012;matching layer1014;carrier layer1016; via1018;non-conductive wall1020; andvertical conductor1022. Anysuitable transducer element1002 can be used including single crystal elements or transducer elements with multiple transducing members (as illustrated, for example, inFIG. 6 with or without the non-transducing pads.)
• Thebacking layer1012 andmatching layer1014 can be made of the same or different materials. Thebacking layer1012 in the illustrated embodiment is conductive. In an alternative embodiment, the matching layer can be disposed between thetransducer element1002 and thethird metal layer1004. In this alternative embodiment, thematching layer1014 is also conductive.
• In at least some embodiments, thecarrier layer1016,metal layer1006, andcontacts1008,1010 can be any thin film or thick film circuit material. Thecarrier layer1016 can be any suitable non-conductive substrate material including, but not limited to, polymeric materials and ceramic materials. The first metal layer is patterned to form thecontacts1008,1010. This thick or thin film circuit can be bonded to thebacking layer1012 using any technique including, but not limited to, using conductive adhesive, conductive epoxy, and the like. In one embodiment, thecarrier layer1016,metal layer1006, andcontacts1008,1010 are a ceramic thick film circuit.
• Thecontact1008 is electrically coupled to themetal layer1006 through the conductive via1018. Thecontact1010 is coupled to themetal layer1004 through thevertical conductor1022. Thenon-conductive wall1020 insulates thetransducer element1002 from thevertical conductor1022. Thenon-conductive wall1020 andvertical conductor1022 can be attached to the other components using any suitable technique including, but not limited to, using conductive adhesive, conductive epoxy, and the like. In at least some embodiments, the vertical sidewall of thecarrier layer1016 adjacent to thevertical conductor1022 is coated with metal to facilitate coupling thevertical conductor1022 to thecontact1010. Wires to the remainder of the system electronics can be attached to the contact layers1008,1010. This embodiment also lends itself to electrical connection via preformed pads in the modular fitting530 shown inFIG. 5.
• FIG. 16 illustrates another embodiment of atransducer1100. Thetransducer1100 includes atransducer element1102;metal layers1104,1106 with correspondingvertical contact pads1108,1110 for attachment ofwires1112,1114; abacking layer1116; and amatching layer1118.
• FIGS. 17A-17F illustrate one embodiment of a method of making thetransducer1100.Transducer material1102′ is removably disposed on acarrier1120, as illustrated inFIG. 17A. A portion of thetransducer material1102′ is then removed to form one or morevertical slots1122, as illustrated inFIG. 17B. Preferably, the vertical slots are between ½ to ¾ the thickness of thetransducer material1102′. For example, thetransducer material1102′ can be patterned and etched using a positive or negative photoresist material or thetransducer material1102′ can be cut or otherwise diced. Ametal layer1104 is formed over thetransducer material1102′ and within the vertical slot(s)1122, as illustrated inFIG. 17C. Themetal layer1104 can be formed using any suitable method including, but not limited to, electroplating, electroless plating, sputtering, chemical or physical vapor deposition, and the like. Any suitable metal, alloy, or combinations thereof may be used. For example, the metal layer may be formed by plating the surface with Ni/Cr and then with gold. Abacking layer1116 is disposed over themetal layer1104 and thecarrier layer1120 is removed, as illustrated inFIG. 17D.
• One or morevertical slots1124 are then formed in the opposite side of thetransducer material1102′ and then filled with metal, along with the formation ofmetal layer1106, as illustrated inFIG. 17E. Preferably, the vertical slots are between ½ to ¾ the thickness of thetransducer material1102′. As an example, the metal layer may be formed by plating the surface with Ni/Cr and then with gold. Amatching layer1118 is disposed over themetal layer1106 and the construct is then diced apart alonglines1126,1128 to exposecontact layers1108,1110, as illustrated inFIGS. 17F and 16. This embodiment also lends itself to electrical connection via preformed pads in the modular fitting530 shown inFIG. 5.
• The above specification, examples and data provide a description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention also resides in the claims hereinafter appended.

Claims (23)

1. An ultrasound transducer, comprising:

a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy, the transducer element further comprising a first non-transducing pad defined in the transducer element;

a first metal layer substantially disposed over a first surface of the transducer element and over the first non-transducing pad; and

a second metal layer substantially disposed over a second surface of the transducer element.

2. The ultrasound transducer ofclaim 1, further comprising a second non-transducing pad defined in the transducer element and a metal pad disposed over the second non-transducing pad and in electrical communication with the second metal layer

3. The ultrasound transducer ofclaim 2, wherein the metal pad is disposed over a portion of the first surface of the transducer element.

4. The ultrasound transducer ofclaim 3, further comprising a metal via through the transducer element and coupling the metal pad to the second metal layer.

5. The ultrasound transducer ofclaim 3, wherein the metal pad and the first metal layer are separated by an open separation region.

6. The ultrasound transducer ofclaim 2, wherein the first and second surfaces are opposing surface of the transducer element and the metal pad is disposed on a third surface of the transducer element, wherein the third surface is between the first and second surfaces.

7. The ultrasound transducer ofclaim 1, wherein the first metal layer extends beyond the transducer element to provide a contact pad configured and arranged for coupling of a wire to the first metal layer and the second metal layer comprises a portion disposed over the first non-transducing pad and configured and arrange for coupling of a wire to the second metal layer.

8. The ultrasound transducer ofclaim 1, wherein the first metal layer extends beyond the transducer element to provide a contact pad configured and arranged for coupling of a first contact on a modular fitting of a catheter to the first metal layer and the second metal layer comprises a portion disposed over the first non-transducing pad and configured and arrange for coupling of a second contact on the modular fitting of the catheter to the second metal layer.

9. An ultrasound transducer, comprising:

a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy;

a first metal layer substantially disposed over a first surface of the transducer element;

a second metal layer substantially disposed over a second surface of the transducer element, wherein the second surface opposes the first surface;

a backing layer disposed over the second metal layer; and

a third metal layer disposed over the backing layer, the third metal layer defining a first contact and a second contact that are separated from each other;

wherein the first contact is coupled to the first metal layer by a first contact via and the second contact is coupled to the second metal layer by a second contact via.

10. The ultrasound transducer ofclaim 9, wherein the first metal via is disposed along at least a portion of an edge of the transducer element and the backing layer.

11. The ultrasound transducer ofclaim 10, wherein the second metal via is disposed along at least a portion of any edge of the backing layer.

12. The ultrasound transducer ofclaim 10, wherein the second metal via is disposed also along at least a portion of an edge of the transducer element.

13. An ultrasound transducer, comprising:

a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy;

a first thin film circuit comprising a first substrate with metal traces disposed on opposing sides of the first substrate and electrically coupled together, wherein the metal traces are configured and arranged to provide a contact pad on one side of the first substrate and an electrode for providing electrical signals to the transducer element on another side of the first substrate; and

a second thin film circuit comprising a second substrate with metal traces disposed on opposing sides of the second substrate and electrically coupled together, wherein the metal traces are configured and arranged to provide a contact pad on one side of the second substrate and an electrode for providing electrical signals to the transducer element on another side of the second substrate;

wherein the transducer element is disposed between the first and second thin film circuits.

14. The ultrasound transducer ofclaim 13, further comprising a conductive matching layer disposed between the transducer element and the first thin film circuit.

15. The ultrasound transducer ofclaim 14, further comprising a conductive backing layer disposed between the transducer element and the second thin film circuit.

16. An ultrasound transducer, comprising:

a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy;

a carrier substrate comprising a first surface and a second surface opposing the first surface;

a first metal layer disposed on the first surface of the carrier substrate, the first metal layer defining a first contact and a second contact that are separate from each other;

a second metal layer disposed on the second surface of the carrier substrate and in electrical communication with the second contact on the first surface of the carrier substrate;

a third metal layer, wherein the transducer element is disposed between the second metal layer and the first metal layer; and

a conducting structure electrically coupling the first contact with the third metal layer, wherein the conducting structure itself is electrically insulated from the transducer element.

17. The ultrasound transducer ofclaim 16, wherein the carrier substrate, first metal layer, and second metal layer are a thick film circuit.

18. The ultrasound transducer ofclaim 16, further comprising a conductive via through the carrier substrate and electrically coupling the second contact to the second metal layer.

19. An ultrasound transducer, comprising:

a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy, the transducer element further comprising a first surface, a second surface opposing the first surface, and an edge surface between the first and second surfaces;

a first metal layer disposed over the first surface of the transducer element;

a second metal layer disposed over the second surface of the transducer element;

a first contact extending from the first metal layer along a first portion of the edge surface of the transducer element; and

a second contact extending from the first metal layer along a second portion of the edge surface of the transducer element.

20. A method of making an ultrasound transducer, the method comprising:

forming at least one first vertical slot extending from a first surface partway through a transducer element;

disposing metal within the at least one first vertical slot to at least coat exposed surfaces of the transducer element within the at least one first vertical slot;

disposing a first metal layer over the first surface of the transducer element and in contact with the metal disposed within the at least one first vertical slot;

forming at least one second vertical slot extending from a second surface partway through the transducer element, wherein the second surface of the transducer element opposes the first surface of the transducer element;

disposing metal within the at least one second vertical slot to at least coat exposed surfaces of the transducer element within the at least one second vertical slot;

disposing a second metal layer over the second surface of the transducer element and in contact with the metal disposed within the at least one second vertical slot; and

cutting the transducer element through the first and second vertical slots to form an ultrasound transducer with first and second contacts formed from the metal disposed in the first and second vertical slots, respectively.

21. The method ofclaim 20, further comprising disposing a matching layer over the second metal layer.

22. The method ofclaim 20, further comprising disposing a backing layer over the first metal layer.

23. A catheter assembly for an intravascular ultrasound system, the catheter assembly comprising:

a catheter having a longitudinal length, a distal end, and a proximal end, the catheter comprising a lumen extending along the longitudinal length of the catheter from the proximal end to the distal end; and

an imaging core configured and arranged for inserting into the lumen, the imaging core comprising

a rotatable driveshaft having a distal end and a longitudinal length,

at least one transducer mounted to the distal end of the rotatable driveshaft, the at least one transducer configured and arranged for transforming applied electrical pulses to acoustic pulses and also for transforming received echo pulses to electrical pulses, and

a twisted wire cable, the twisted wire cable comprising i) two wires running along the cable and electrically coupled to respective contacts of the at least one transducer, and ii) a shield extending along the cable and within which a portion of the two wires are disposed.

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